The present invention generally relates to containers and, more specifically, to sift proof containers designed to prevent leakage of particulate contents or infestation by insects.
Many containers, such as cartons, boxes or other less rigid containers, are constructed from paper-based materials and include open ends having a plurality of flaps. These containers are usually folded from a flat condition into an erected condition, after which a desired product may be introduced into the container. The flaps are then folded and connected together, typically using an adhesive, to close the ends of the container.
Particulate products, such as granulated or powdered products, require packaging that will prevent leakage of the product during shipment and storage. Plastic liners may be used inside cartons or boxes for this purpose, however, such liners increase packaging costs. To reduce costs, linerless sift proof containers have been developed to store and ship particulate products. The end flaps of these sift proof containers must be tightly sealed in a manner that prevents the contents from sifting out between the flaps. With typical sift proof containers, opposite minor end flaps are first folded down, followed by a first major flap and then a second major flap. Typically, all of the flaps receive adhesive deposits in the form of intermittent or continuous adhesive beads to ensure that the seams between the various flaps are sealed in a sift proof manner. In the case of food products, this also prevents insects from entering the sealed container.
As the development of sift proof containers has progressed, certain problems have been addressed relative to increasing sift proof seal integrity and reducing costs associated with adhesive and paper product. One manner of reducing the required amount of adhesive and simultaneously improving the integrity of the sift proof seal has been through the use of embossments on the various flaps. Raised embossments provide opposed surfaces of the flaps lying in closer relation and, therefore, the usual gap between the flaps does not need to be filled with as much adhesive. Also, a momentary decrease in the volume of dispensed adhesive during packaging will be less likely to compromise the integrity of the seal. Prior sift proof containers have also included a modified first major flap that enables direct contact between embossed portions of the minor flaps and a corresponding embossed portion of the second major flap. This more effectively prevents leakage of particulate product and reduces the amount of adhesive and paper product used in constructing the container.
Despite the various developments in the area of sift proof containers, improvements are still needed to increase sift proof seal integrity, reduce adhesive requirements and reduce product contamination by adhesive. In these regards, even the more recently developed sift proof containers have used adhesive beads that extend completely across both minor flaps. This requires the minor flaps to directly abut one another when folded into closed positions. If a gap is left between the minor flaps, the adhesive applied across the minor flaps can drop into the container and contaminate the contents. Increasing the size of the minor flaps increases the amount of paper product and adds to the expense of the container. Also, the use of adhesive extending completely across the minor flaps increases the amount of adhesive and likewise increases the associated packaging costs.
The present invention provides a sift proof container including a sidewall enclosing an interior space. The container includes at least one open end having a plurality of flaps. The flaps comprise first and second minor flaps and first and second major flaps. The minor flaps have opposed edges when folded inwardly to their respective closed positions and the major flaps are configured. to be folded inwardly to respective closed positions over the minor flaps. The first major flap includes opposite side edges that are recessed with respect to sidewall portions of the container. These side edges are positioned adjacent to respective corners of the minor flaps. The second major flap includes at least three free edges and a fourth edge connected with the sidewall. Adhesive is positioned proximate the three free edges of the second major flap to seal against the first major flap and the minor flaps when the minor and major flaps are folded to their closed positions. Initially, adhesive may be placed along two opposite side edges of the second major flap or along hinged edges of the minor flaps.
In one aspect of the invention, a pair of separate adhesive deposits are made on outer surfaces of the corners of the minor flaps that mate with the first major flap. These separate adhesive deposits extend only partially toward the opposed edges of the first and second minor flaps when the first and second minor flaps are folded to their closed positions. This significantly reduces the amount of adhesive used to construct the sift proof container. This aspect of the invention also prevents contamination of product within the container by adhesive. The pair of separate adhesive deposits may alternatively or also be made on an inner surface of the first major flap at opposite corners thereof adjacent to the respective corners of the first and second minor flaps. To achieve similar benefits, this pair of separate adhesive deposits also extends only partially toward the opposed edges of the first and second minor flaps when the first and second minor flaps are folded to their closed positions.
In the preferred embodiment, at least one of the second major flap and the first and second minor flaps have embossments positioned between the sidewall and the recessed side edges when the minor and major flaps are folded to their closed positions. As part of this aspect of the invention, the adhesive positioned proximate at least two of the free edges contacts the embossments when the minor and major flaps are folded to their closed positions. The first major flap includes opposite corner portions connected with the sidewall and each of the opposite, recessed edges more specifically extends inward to define one edge of each of the corner portions. The separate adhesive deposits are substantially confined to the corner portions when the minor and major flaps are folded to their closed positions.
More specifically, both the minor flaps and opposite edge portions of the second major flap can have raised embossments that mate with each other in the closed positions. The raised embossments end at the corner portions to provide a nesting space for the first minor flap and the separate adhesive deposits are substantially confined within this nesting space. As another aspect of the invention, inner opposed edges of the first and second minor flaps may be spaced a substantial distance apart when folded to their closed positions and, because of the use of separate adhesive deposits as described above, adhesive will not fall through the gap between the minor flaps into the container. The adhesive positioned proximate the three free edges of the second major flap may include separate or continuous adhesive beads or other types of adhesive deposits that result in a caulking seal with the respective minor flaps and the first major flap.
The invention further contemplates methods of folding and sealing a plurality of flaps disposed about the open end of a container to construct a sift proof container. These methods generally involve folding and sealing a container as described above. In addition to the advantages described above, the methods described herein may be performed using typical packaging machinery. As less adhesive may be used in carrying out the present invention, the methods described herein may be performed in a more cost effective manner.
Additional advantages, objects and features of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.